WHAT is Vince Cable up to? The ballroom dancing, book- flogging, Tory-loathing Lib Dem is on manoeuvres.

Last week, Saint Vince made an audacious power grab, declaring he is running a "department for economic affairs".

He isn’t. But he’d like to. And his game seems to be pushing his luck with a kind of soft, low-level warfare against the coalition.

Cam and Nick Clegg may be still enjoying some kind of love-in at 10 Downing Street. But it’s not contagious. The Lib Dem left think it’s dangerous — and doomed. And St Vince wants to be seen as unofficial leader of the anti-Tory resistance.

He did not want this coalition. He tried everything to stop it, calling Gordon Brown in a desperate bid to do a Lib-Lab deal. Plenty of Lib Dems agree.

But what can they do if their leader, Clegg, is wandering around like a triumphant teenager who just scored the 31st notch on his bedpost?

The answer: Rally behind St Vince. Aged 67 and a former Chief Economist at Shell, he resents being bossed about by the 39-year-old George Osborne.

Now that David Laws is gone, he sees himself as the new Alpha Male of the Lib Dems (not, I admit, a hotly-contested category)

Osborne, who yesterday triumphed at the G20 summit by winning blessing for his cuts, isn’t rising to the bait.

When Cable tried to make out HE is in charge of regulating the banks, Osborne quietly ignored him.

Then Vince tried again last week, saying his business department somehow shared economic responsibility with the Treasury. "Two departments working in parallel," he claimed.

In his dreams. His non-job is to run the pretty pointless Dept for Business, Innovation & Skills.

Until recently, Vince himself argued the department was so useless it could be abolished and no one would notice.

Hard for him, now, to make it a power base. But he can use his Cabinet perch to argue for harder taxes, and softer cuts.

Neither Clegg nor Cameron quite trust Cable. That is why, for all his popularity, he remains caged in an obscure department.

It hasn’t taken him long to start rattling this cage. He might do so again when the cuts are announced in next month’s emergency budget. The question is: how many Lib Dems will join him?

"The Lib Dems are far more divided than we are," a Tory Cabinet member tells me. "They always split over coalition."

This is what many Tories hope. That the Lib Dems will split — so the Tories gobble up the right-wing Lib Dem MPs.

The title of Cable’s latest book — his memoir — is Free Radical. That’s how he sees himself. Not as a bloke taking orders from a Tory.

I reckon that he’s writing an updated version inside his head. One with an explosive ending.

If he does try to split the Lib Dems, he will make history. By playing straight into the Tories’ hands.